Die set assembly



April 25, 1961 J. c. DANLY 2,981,569

DIE SET ASSEMBLY Filed Dec. 12, 1956 INVENTOR Jn/255 7. DAM. Y

www A oRNEY DIE SET ASEMBLY James C. Danly, River Forest, lll., assignor to Danly Machine Specialties, Inc., Chicago, Ill., a` corporation of Illinois Filed Dec. 12, 1956, Ser. No. 627,867l

`6 Claims. (Cl. 30S- 6) My invention relates to a die set assembly and more particularly to a die set assembly which embodies an improvement over die set assemblies of the prior art.

The die set assembly of a power press includes a punch holder carried by the press slide and a die holder supported on the press bed. In the course of an Operation of the press, the punch holder and die holder move toward each other. The gibs which support` the press slide for reciprocation in the press frame permit a certain misalignment between the slide and the bed. This misalignment may, for example, be of the order of 0.005 inch. In order that a satisfactory operation be performed, it is necessary that the press punch and die be more accurately aligned. In the prior art the die holder carries guideposts adapted to enter into bushings carried by the punch holder as the holders move toward each other to hold `the misalignment between the punch and die to within a predetermined tolerance. For example, these bushings and guideposts may be required to hold the misalignment to within a tolerance of 0.0005 inch.

Ball bushings recently have come into use in die set assemblies to cooperate with the die set guideposts to hold the misalignment between the punch and die to within the required tolerance. I have found that if a relatively large misalignment within that permitted' by the press gibs exists, the balls of a ball bushing score or groove the guideposts inreducing misalignment. This yscoring or grooving results from the point contact between the balls andthe post as the post enters the ball bushing. Obviously with this operation the posts must be replaced at relatively frequent intervals` if prope operation of the press is tobe achieved.` n

I have invented an improved die set assembly which reduces the wear on the assembly guideposts. My assembly substantially eliminates the grooving ofthe guideposts in the course of operationof the press. It increases the life of the die set guideposts. t V

One object of my invention is to provide an improved die set assembly which reduces wear .onthe die set guideposts. t v

Another object of my invention is to provide an im# proved die set assembly which substantially eliminates the tendency of a ball bushing to score or groove the die set guideposts.

A further object of my invention is to provide an improved die set assemblytwhich increases the life of the die set guideposts'. i

Other and further objects of my invention will appear from the following description.

`In general, my invention contemplates the provision oa die set assembly including a diet'holder` carrying guideposts and a punch holder carrying `ball bushings t adapted to receive the guideposts when the punch holder and die holder are moved toward each other in the course of a press operation. I securea guide bushing having an inner diameter slightly larger than the diameter of a post to the punch holder to guide the'post injits entry `er 12 and die holder 14 move toward each other.

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misalignment between the press punch and die to within a tolerance which is slightly greater than the required tolerance. The ball bushing reduces the misalignment from this tolerance to within the required tolerance. The amount of reduction of the misalignment provided by my guide bushing is such that the amount of strain of the guidepost when it encounters a ball of the ball bushing is within the elastic limit of the material of which the post is formed. As a result, the guidepost will not be scored or grooved in the course of a press operation. My guide bushing also serves to retain the ball bushing in the punch holder.

In the accompanying drawings which Vform part of the instant specication and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

Figure 1 is a perspective view of my improved die set assembly.

vFigure 2 is a fragmentary sectional view of my improved die set assembly, drawn on an enlarged scale and taken along the line 2-2 of Figure 1.

`Figure 3 is a sectional view of my improved die set assembly, taken along the line 3 3 of Figure 2.

Figure 4 is a perspective view of the guide bushing of my improved die set assembly.

Figure 5 is a fragmentary perspective view of a guide- -post showing the manner in which the post is scored in assemblies of the prior art.

YMore particularly, referring now to the drawings, my improved die set assembly, indicated generally by the reference character 10, includes a punch holder 12, adapted to ibei secured to the slide (not shown) of a power press, and a die holder 14, which is to be supported `by the press bed (not shown). As is known in the art, in the course of a press operation the punch hold- In order to reduce the misalignment permitted by the press gibs to within a predetermined tolerance, die holder 14 carries. a number of guideposts 16 screwed into or otherwise secured to the die holder 14. I dispose a number of ball bushings indicated generally by the reference character 18 in respective bores 20 `formed in punch holder 12. The ball bushings 18 have many `advantages over the plain sliding` bushings formerlyemployed. They reduce friction between the guideposts and the bushings. A

They permit an unlimited travel of the post within the bushing without regard to the length of bushing ernployed. `These and other advantages make the use of these ball bushings desirable.

Each of the ball bushings 18 has an outer cylindrical sleeve 22 disposed in a bore 20. Any suitable means, such as screws 24, or the like, secure respective ball guides 26 to sleeve `22 to form the inner sides of a number of ball circuits.V A ball retainer 23` disposed within the sleeve 22 hasa number of elongated openings 30 which dene the outer` sides of the ball circuits for the `balls 32 of the bushing. Respective rings 34 and 36 held over the ends of the retainer 2S by respective caps 38 and 40 attached to the sleeve 22` hold retainer 28 within sleeve 22. The `contours of the guides 26 and the openings 30` are `such that balls 32 are retained within their' circuits. t A

When the punch holder 12 and die holder I14 move toward each other in the course; of a pressoperation, the post `16 engages `certain ofthe balls 32 to roll the balls between the post andthe inner surface ofthe cylindrical sleeve 22. The inner surface of sleeve 22 has a plurality of vertical grooves 42 which provide return paths `for the balls of' each circuit. It will be appreciated that each ball` circuit-includes one leg of` loaded balls which roll `between the outer surface of post 16 and the inner surinto the ball bushing. My guide bushing rednces the` face of cylinder` 22.. Each ball circuitalsoincludes a leg of unloaded balls Itraveling downwardly, as viewed in the figures, along a path provided by a groove 42. Y Y

As has been explained hereinabove, the press gibs (not shown) permit a certain misalignment between the punch and die of the press. As a post 16 enters the bushing 18, it makes point contact rwith one or more of the balls 32. It can be demonstrated that if the misalignment between the punch and dieis over a predetermined value and yet within the amount permitted by the press gibs, the compressive stress between a ball 32 and the post 16 will produce a strain which is over the elastic limit of the material of which the post 16 is formed. When this occurs, the post is scored or grooved. Scores or grooves which may be formed in a post 16 in the manner described are indicated by the reference character 44 in Figure 5.

I provide my improved die set assembly with a number `of plain guide bushings 46 for guiding the posts 16 in their entry into the ball bushings 18. Each bushing 46 is formed with a bore 4S having a diameter which is greater by a predetermined amount than the diameter of the corresponding post 16. These guide bushings 46 reduce the misalignment between the punch and die to an amount which is slightly greater than the desired tolerance. For example, if the press gibs permit a misalignment between the punch and die of about 0.005 inch, the diameter of the bushings 46 is such as will reduce this misalignment to within 0.001 inch. It is to be noted that contact between the post 16 and the bushing 46, as the die holder and punch holder move toward each other, is not a point contact, but is distributed over a relatively wide area. As a consequence, the stress per unit area is much less than the stress per unit area which occurs in the prior art where the post makes its initial contact with a. ball. The misalignment between the punch and die is reduced by bushings 46 to an amount such that the strain resulting from contact between a post 16 and the balls 32 of a bushing `18 will not exceed the elastic limit of the post 16. As a result, in the iinal reduction of misalignment produced by the bushing 18 no scoring or grooving of post 16 occurs. If the bushings 46 reducek misalignment to, for example, within 0.0011 inch, the ball bushings 18 are required only to reduce this misalignment to within a desired tolerance of, for example, 0.0005 inch.

I form the bushing 46 with an annular recess 50 surrounding the bore 48. The recess 50 is adapted to receive an end of the ball bushing 1S extending beyond Vthe surface of the punch holder 12. A snap ring 52 disposed in correspondingly located grooves in the bushing 46 and in the sleeve 22 of bushing 18 holds the ball bushing 18 and the guide bushing 46 assembled.

I provide my improved die set assembly with a number of clamps 54 for holding the bushing assemblies in the bores 2t) in the punch holder 12. Each clamp 54 has a tongue 56 which engages an annular groove 53 formed in the outer surface of bushing 46. Bolts 60 pass through bores in the clamps and are threaded into the punch holder 12 to hold the bushing 46 rmly against the punch holder.

In operation of my improved die set assembly, as the punch holder 12 and die holder 14 move toward each other in the course of a press operation, the posts 16 rst enter guide bushings 46. As is explained hereinabove, these bushings 46 reduce misalignment between the punch and die to an amount which is slightly greater than the desired misalignment tolerance. This operation results from a surface contact between the p ost and the bushing ov'er a relatively large area, with the result that the posts are not strained beyond their elastic limit. After this initial reduction of misalignment, the ball bushings 18 are'required only to reduce the misalignment a small amount. Since the bushings 18 are required only to reducevthe tolerance a4 small amount,vthe strain owing to the stress resulting from the point contact between a ball 32 and the post 16 will not exceed the elastic limit of the material of which the post is formed. No scores or grooves will be formed in the post. Itis to be noted that the bushings 46 accomplish their result of preventing ex- Y cessive Wear on the posts 16 while permitting `advantage to be taken of the desirable features of the ball bushings. Once the posts 16 have engaged the ball bushings 18, misalignment is reduced to an extent that the posts noV longer are in frictional engagement with entry bushings 46. The friction resulting from the use of my improved die set assembly is much less than that which is incident to the use of plain bushing die set assemblies of the prior art. Further, my assembly permits unlimited travel of the posts 16, with the result that the bushing length need not vary with the length of stroke of the press.

It will be seen that I have accomplished the objects of my invention. I have provided an improved die set assembly which prevents excessive wear on the die set guideposts. My lassembly permits use of ball bushings without the formation of grooves or scores such ias |are formed in the prior art. My assembly ensures a long life for the guideposts of the die set.

It will be understood that certain features and subcombinations are of utility and may be employed without reference t0 other features `and subcombinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be undestood that my invention is not to be limited to the specific details shown yand described.

Having thus described my invention, what I claim is:

1. A die set assembly for a power press having a pair of relatively movable members including in combination a die holder carried by one of said relatively movable members for movement therewith, a punch holder carried by the other one of said relatively movable members for movement therewith, said die holder and said punch holder being moved toward each other as said relatively movable members move toward each other during a press operation, a guidepost carried by one of said die holder and punch holder, a ball bushing for receiving said guidepost when said die holder and said punch holder move toward each other and a means for guiding said post in the course of its entry into said ball bushing. f

2. A die set assembly as in claim 1 in which the one of said die holder and punch holder carrying said bushing is formed with a bore', said bushing being disposed in said bore, and including means for securing said guide means to said one of said holders to retain said bushing in said bore. Y

3. A die set assembly for a'power press having a pair of relatively movable members including in combination a die holder, `a punch holder, said die holder and said punch holder being carried by the respective relatively movable members for movement therewith to be moved toward each other as said relatively movable members move toward each other during a press operation, a guidepost carried by one of said die holder and said punch holder, a ball bushing for receiving said guidepost when said die holder and said punch holder move toward each other to reduce potential misalignment between said die and punch holders to within a predetermined tolerance and a means for guiding said post in its entry into said bushing to reduce the misalignment of said holders to within a tolerance which is greater than said predetermined tolerance.

4. A die set assembly as in claim 3 in which said post is a cylindrical post having a predetermined diameter, said guide means being annular and having a diameter greater by a predetermined lamount .than said post di ameter. g Y

5. A die set assembly for a power press having a pair of relatively movable members including in combination 5 die holder, a punch holder, said die holder and said punch holder being carried by the respective movable members for movement therewith to be moved toward each other as said relatively movable members move toward each other during a press operation, a guidepost carried by one of said holders, the other of said holders being formed with a bore, a ball bushing removably disposed in said bore, said ball bushing for receiving said post when said holders move toward each other, a guide member for guiding said post in its entry into said bushing and means for securing said guide member to said other holder to retain said bushing in said bore.

6. A die set assembly as in claim 5 including means 6 for connecting said bushing and said guide member for movement as a unit.

References Cited in the file of this patent UNITED STATES PATENTS 1,787,476 Gattrell Ian. 6, 1931 2,238,302 Baumbach Apr. 15, 1941 2,317,889 Danneman Apr. 27, 1943 lo 2,422,774 Conner lune 24, 1947 2,422,775 Conner June 24, 1947 2,523,358 Conner Sept. 26, 1950 2,694,130 Howard Nov. 9, 1954 2,749,987 Janiszewski llune 12, 1956 

